My N Scale Metra MP36PH 427 locomotive made an unsual, grinding noise which is unlikely not supposed to happen. When I took it to my local hobby shop, they told me that the inside of the locomotive's trucks are covered in carpet and there was a middle gear that was popped out of place.
So the most important thing about Model Railroading in general is take care of your locomotives; whether if it's steam and/or diesel (especially steam locomotives). It can save you money and you may never know if there will be left over parts to fix them. Also, I wouldn't recommend a model railroad on carpet which can get inside your locomotive(s). It would be better if the tracks would have a smooth, stable surface. Lastly, if you have nothing else to do with your model railroading, it's not a bad idea to get other locomotives and/or rolling stock so they can be used for backups.
